Needle thread wiper and pull-back mechanism for sewing machines

ABSTRACT

A needle thread wiper and pull-back comprising a simple linkage carried by the sewing head face plate and actuated by a single rotary solenoid and including provision for regulating the action of the pull-back to accommodate changes in work fabrics and sewing threads.

United States Patent 1191 Rogner [451 Nov. 12, 1974 1 NEEDLE THREAD WIPER AND PULL-BACK MECHANISM FOR SEWING MACHINES [75] Inventor:

[73] Assignee: The Singer Company, New York,

[22] Filed: Jan. 21, 1974 [21] Appl. No.: 435,373

Gerd Rogner, Karlsruhe, Germany [52] U.S. Cl. 112/252, 112/242 [51] Int. Cl. D05b 65/00, DOSb 49/00 [58] Field of Search 112/65, 74, 241-248,

[56] References Cited UNITED STATES PATENTS 1,876,538 9/1932 Althens 112/255 X 2,251,676 8/1941 Gunther 112/252 X 2.354.559 7/1944 Thornton 112/252 X 3,308.776 3/1967 lvanko et a1. 1. 112/252 X 3.584.589 6/1971 Pirrello 112/252 3,640,236 2/1972 Nicoluy 112/243 Primary ExaminerWerner H. Schroeder Attorney, Agent, or Firm-E. L. Bell; Robert E. Smith;

Marshall J. Breen [57] ABSTRACT A needle thread wiper and pull-back comprising a simple linkage carried by the sewing head face plate and actuated by a single rotary solenoid and including provision for regulating the action of the pull-back to accommodate changes in work fabrics and sewing threads.

3 Claims, 4 Drawing Figures alt 347L102 PATENTEI] IIUV 1 2 I974 NEEDLE THREAD WIPER AND PULL-BACK MECHANISM FOR SEWING MACHINES BACKGROUND OF THE INVENTION It is well known in the sewing machine art to provide a thread wiper for withdrawing the severed end of needle thread out of the work at the completion ofa stitching operation. If the severed end of needle thread becomes caught in the work piece, the needle thread end is apt to be drawn out therewith when the work piece is withdrawn thus causing an abnormally long and unsightly starting needle thread end on the succeeding workpiece. A needle thread end must be preserved long enough to provide for initiation of sewing on the succeeding work piece without danger of unthreading of the needle, and, therefore, prior thread wipers were required to have sufficient movement and capacity for removing the largest length of thread from the work that could conceivably be required by any possible combination of work thickness and thread characteristics.

BRIEF SUMMARY OF THIS INVENTION It is an object of this invention to provide a thread wiper for the needle thread of a sewing machine which has a relatively small movement of fixed stroke but which can operate successfully under differing conditions of work fabrics and sewing thread characteristics. This object of the invention is attained by the provision of an adjustable thread pull-back mechanism operatively connected with the thread wiper mechanism and effective to draw back through the needle eye a suffi cient length of the thread end so that the thread wiper of fixed stroke can withdraw the remaining thread end from the work. When the thread wiper and pull-back are retracted at the start of a succeeding sewing operation, the thread drawn back by the pull-back is made available to the stitch forming instrumentalities so that danger of unthreading of the needle eye is obviated.

DESCRIPTION OF THE DRAWING The accompanying drawing illustrates a preferred embodiment of this invention in which:

FIG. 1 represents an end elevational view of a sewing machine having a thread wiper and pull-back device of this invention applied thereto and shown in a retracted inoperative position as during a sewing operation,

FIG. 2 represents an end elevational view of the sewing machine of FIG. 1 but showing the thread wiper and pull-back device of this invention in an operative positron,

FIG. 3 represents a front elevational view of the sewing machine of FIG. 1, and

FIG. 4 represents an elevational view of the inside of the end cover plate of the sewing machine showing the thread wiper and pulleback mechanism thereon.

Referring to the accompanying drawing ll denotes a sewing machine frame which may comprise a work supporting bed 12 from which rises a standard 13 supporting a sewing head 14 above the bed. A thread carrying needle 15 is endwise reciprocable in the sewing head and passes through a needle aperture in a throat plate 16 on the bed in cooperation with a loop taker 17 carried beneath the bed in the formation of lock stitches. A presser foot 18 carried in the sewing head presses a work fabric 19 against the throat plate 16 so that it may be penetrated by the needle as the sewing progresses.

In the accompanying drawing, the needle thread which is indicated at 20, is shown, directed as is conventional in lock stitch sewing machines first to a thread tensioning device 21 on the sewing head, then to a check spring 23, next to a take-up member 23, and then through thread guides 24 and 25 on the sewing head and a thread guide 26 on the needle clamp 27 to the needle eye.

The needle thread wiper and pull-back mechanism of this invention is adapted for use with a sewing machine in which, at the completion of a stitched seam, the needle thread is severed beneath the work supporting bed. Many underbed thread trimmers are known for accomplishing such thread severing operations, any of which may be used in carrying out the present invention. In FIG. 1 a needle thread catching and severing arm 30 is illustrated beneath the throat plate and above the loop taker and is indicative of the operative element of any known underbed thread trimmer. For instance, the element 30 may comprise the thread catching finger of a trimming mechanism organized in accordance with the principle of the US. Pat. No. 3,524,420, dated Aug. 18, 1970 which is incorporated herein by reference.

It will be noted, as shown in FIGS. 1 and 3, that when the needle thread is severed beneath the throat plate by an underbed thread trimmer, the thread end after sev erance will remain extending through the work fabric 20 and is apt to become caught in the work and distended if the work fabric is removed before the thread end is withdrawn therefrom.

The needle thread wiper and pull-back'mechanism of this invention is preferrably carried inside an end cover plate 39 which closes the free end of the sewing head 14. The actuation for the thread wiper and pull-back mechanism may be derived from a rotary solenoid 40 carried in the end cover plate 40 which when actuated rotates a solenoid shaft 41 to which is clamped a radially extending arm 42 carrying a crank pin 43. Preferrably the rotary solenoid includes a return spring and internal stops (not shown) so that the crank pin 43 will automatically return to a predetermined position when the solenoid is not energized and when actuated, the solenoid will drive the crank pin 43 through a predetermined angle.

Pivoted on a fulcrum pin 44 near the lower extremity of the end cover plate is a bell crank lever 45 which has secured on one arm 46 a thread wiper 47 which may take the form of a wire ordinarily disposed behind the path of the needle and terminating in a laterally offset extremity 48 which extends perpendicularly across the path of the needle thread 20. The other arm 49 of the bell crank lever 45 is pivotally connected as at 50 to a link 51 which extends upwardly and embraces the crank pin 43.

It will be appreciated, therefore, that the stroke imparted to the thread wiper 47 upon each actuation of the rotary solenoid 40 will be of uniform angular extent and that such stroke will carry the wiper extremity 48 position as ilcent to the thread guide 24 and including a laterally offset thread engaging finger 61 which extends transversely across the thread path and terminates in a down turned tang 62 to prevent the thread from slipping off. Preferrably the thread pull-back lever 60 is supported on fulcrum pin 63 carried by a bracket 64 which is fixedly secured inside the end cover plate 40.

The thread pull-back lever 60 is formed with a slot 65 which is elongated in the direction radially of the fulcrum pin 63 and along which slot may be clamped a shouldered pivot pin 66 by which a link 67 is connected to the thread pull-back lever 60. The other extremity of the link 67 is pivotally connected to the link 51 by a pivot pin 68 which may similarly be clamped in a selected position along a slot 69 formed lengthwise along the link 51.

By adjusting the position of the pivot pin 68 along the slot 69, the inoperative or at rest position of the thread pull-back lever may be regulated and this preferrably should be set as shown in FIGS. 1 and 3 so that the thread engaging finger 61 extends out of contact with the needle thread above the thread guide 24. In the embodiment illustrated in the drawing, this adjustment can be made only by removing the end cover plate from the sewing machine.

By adjusting the position of the pivot pin 66 along the slot 65, the stroke of the pull-back lever may be regulated. As shown in FIG. 2, the thread engaging finger 61 moves across the path of the needle thread 20 and downwardly over the thread guide 24 to create a loop of thread 80 when the solenoid is energized; and by adjustment of the position of the pivot pin 66 along the slot 65, the size of the loop thread 80 may be regulated.

As shown in FIG. I, the end cover plate 39 may be formed with an aperture 81 which is in registration with the slot 65 in one extreme position of the thread pullback lever 60 and through which aperture adjustment of the pivot pin along the slot 65 may be effected from externally of the sewing machine.

Having thus described the nature of the invention,

what we claim herein is: 1. In a sewing machine having a work support and a sewing head carried above said work support and fitted with an end cover plate, a loop taker arranged beneath said work support, a thread carrying needle supported within said sewing head for endwise reciprocation through the work support in cooperation with the loop taker in the formation of stitches, a needle thread takeup mechanism arranged in the sewing head, and thread trimming mechanism effective to sever the needle thread beneath said work support, mechanism for withdrawing a severed needle thread above the work support comprising a thread wiping arm pivotally mounted within said sewing head end cover plate to swing in an arc traversing the path of the needle thread between said needle and said work support, an actuator for said thread wiping arm, operating mechanism connecting said thread wiping arm to said actuator for imparting movement in a fixed throw to said thread wiping arm, a thread pull-back lever fulcrummed within said end cover plate to swing in an arc traversing the path of the needle thread between said needle thread take-up mechanism and said needle, an operating link for said thread pull-back lever having a connection with said thread wiper operating mechanism and a pivotal connection with said thread pull'back lever, at least one of said connections being adjustable and accessible through an opening in said sewing head end cover so that a change in the stroke of the thread pull-back lever may be effected from externally of the sewing machine.

2. The combination as set forth in claim 1 in which said actuator comprises a rotary solenoid carried by said end cover plate.

3. The combination as set forth in'claim l in which the pivotal connection of said operating link with said thread pull-back lever comprises a pivot pin with clamp means for securing said pivot pin at a selected distance from the fulcrum of said thread pull-back lever. 

1. In a sewing machine having a work support and a sewing head carried above said work support and fitted with an end cover plate, a loop taker arranged beneath said work support, a thread carrying needle supported within said sewing head for endwise reciprocation through the work support in cooperation with the loop taker in the formation of stitches, a needle thread take-up mechanism arranged in the sewing head, and thread trimming mechanism effective to sever the needle thread beneath said work support, mechanism for withdrawing a severed needle thread above the work support comprising a thread wiping arm pivotally mounted within said sewing head end cover plate to swing in an arc traversing the path of the needle thread between said needle and said work support, an actuator for said thread wiping arm, operating mechanism connecting said thread wiping arm to said actuator for imparting movement in a fixed throw to said thread wiping arm, a thread pull-back lever fulcrummed within said end cover plate to swing in an arc traversing the path of the needle thread between said needle thread take-up mechanism and said needle, an operating link for said thread pull-back lever having a connection with said thread wiper operating mechanism and a pivotal connection with said thread pull-back lever, at least one of said connections being adjustable and accessible through an opening in said sewing head end cover so that a change in the stroke of the thread pull-back lever may be effected from externally of the sewing machine.
 2. The combination as set forth in claim 1 in which said actuator comprises a rotary solenoid carried by said end cover plate.
 3. The combination as set forth in claim 1 in which the pivotal connection of said operating link with said thread pull-back lever comprises a pivot pin with clamp means for securing said pivot pin at a selected distance from the fulcrum of said thread pull-back lever. 